This invention relates to devices for the inspection and repair of piping, such as fluid distribution mains, especially including underground natural gas pipelines.
Gas distribution mains typically include many 90 degree corners, and in most of the United States, are of diameters not greater than four (4) inches.
Currently there is no known method of moving inspection and repair instrumentation through a distribution main that makes turning the 90 degree corners possible. This is especially true for mains of diameters four inches or less. Internal inspection of mains is limited to the point of being economically impractical, except with highly specialized equipment in very limited situations. Most of the specialized equipment requires that service to customers be interrupted.
A device known as the Chicago Leak Locator is used by Peoples Coke, Light, and Gas Company of Illinois to find difficult-to-pinpoint leaks in low pressure gas distribution systems. This device is only useful in mains where gas is supplied from both ends of the main, in order to prevent loss of gas service to customers. A stiff sewer rod is required to move the Locator, and the rod does not permit passage of the device around corners in mains.
There are tools available for use inside of mains. However they also suffer from inability to turn corners, which limits the distance the tools can go. AMF Tuboscope has designed and built a model of a survey tool for use in four inch distribution lines. This tool has not met with success, partly because of its inability to turn corners or move past siphon drips and service tees extending into the interior of a main.